Search

La ganadería bovina es una de las principales fuentes de emisiones antropogénicas de gases de efecto invernadero (GEI). A nivel internacional, regional y nacional existe una gran diversidad de estudios relacionados con la búsqueda de estrategias de mitigación de esos gases. El objetivo de este trabajo fue analizar el efecto de la aplicación de tecnologías estratégicas sobre las emisiones de GEI en sistemas productivos ganaderos típicos de la región sur de San Luis. Para ello se analizaron 6 casos de estudios en sus características actuales (SPA) y se plantearon y simularon dos propuestas mejoradoras de sus sistemas productivos (SPM1 y SPM2), se estimaron emisiones de CH. por fermentación entérica y N.O de suelos gestionados. Se caracterizaron las emisiones y se realizó una comparación de emisiones de GEI de los sistemas entre sus tres estados (SPA, SPM1 y SPM2) a través de un ANOVA. Las “emisiones por ternero” fueron significativamente superiores (P

Billions of people rely on groundwater as being an accessible source of drinking water and for irrigation, especially in times of drought. Its importance will likely increase with a changing climate. It is still unclear, however, how climate change will impact groundwater systems globally and, thus, the availability of this vital resource. Groundwater recharge is an important indicator for groundwater availability, but it is a water flux that is difficult to estimate as uncertainties in the water balance accumulate, leading to possibly large errors in particular in dry regions. This study investigates uncertainties in groundwater recharge projections using a multi-model ensemble of eight global hydrological models (GHMs) that are driven by the bias-adjusted output of four global circulation models (GCMs). Pre-industrial and current groundwater recharge values are compared with recharge for different global warming (GW) levels as a result of three representative concentration pathways (RCPs). Results suggest that projected changes strongly vary among the different GHM–GCM combinations, and statistically significant changes are only computed for a few regions of the world. Statistically significant GWR increases are projected for northern Europe and some parts of the Arctic, East Africa, and India. Statistically significant decreases are simulated in southern Chile, parts of Brazil, central USA, the Mediterranean, and southeastern China. In some regions, reversals of groundwater recharge trends can be observed with global warming. Because most GHMs do not simulate the impact of changing atmospheric CO2 and climate on vegetation and, thus, evapotranspiration, we investigate how estimated changes in GWR are affected by the inclusion of these processes. In some regions, inclusion leads to differences in groundwater recharge changes of up to 100 mm per year. Most GHMs with active vegetation simulate less severe decreases in groundwater recharge than GHMs without active vegetation and, in some regions, even increases instead of decreases are simulated. However, in regions where GCMs predict decreases in precipitation and where groundwater availability is the most important, model agreement among GHMs with active vegetation is the lowest. Overall, large uncertainties in the model outcomes suggest that additional research on simulating groundwater processes in GHMs is necessary.

WaterGAP is a global hydrological model that quantifies human use of groundwater and surface water as well as water flows and water storage and thus water resources on all land areas of the Earth. Since 1996, it has served to assess water resources and water stress both historically and in the future, in particular under climate change. It has improved our understanding of continental water storage variations, with a focus on overexploitation and depletion of water resources. In this paper, we describe the most recent model version WaterGAP 2.2d, including the water use models, the linking model that computes net abstractions from groundwater and surface water and the WaterGAP Global Hydrology Model (WGHM). Standard model output variables that are freely available at a data repository are explained. In addition, the most requested model outputs, total water storage anomalies, streamflow and water use, are evaluated against observation data. Finally, we show examples of assessments of the global freshwater system that can be achieved with WaterGAP 2.2d model output.

In global hydrological models, groundwater storages and flows are generally simulated by linear reservoir models. Recently, the first global gradient-based groundwater models were developed in order to improve the representation of groundwater–surface-water interactions, capillary rise, lateral flows, and human water use impacts. However, the reliability of model outputs is limited by a lack of data and by uncertain model assumptions that are necessary due to the coarse spatial resolution. The impact of data quality is presented in this study by showing the sensitivity of a groundwater model to changes in the only available global hydraulic conductivity dataset. To better understand the sensitivity of model output to uncertain spatially distributed parameters, we present the first application of a global sensitivity method for a global-scale groundwater model using nearly 2000 steady-state model runs of the global gradient-based groundwater model G3M. By applying the Morris method in a novel domain decomposition approach that identifies global hydrological response units, spatially distributed parameter sensitivities are determined for a computationally expensive model. Results indicate that globally simulated hydraulic heads are equally sensitive to hydraulic conductivity, groundwater recharge, and surface water body elevation, though parameter sensitivities vary regionally. For large areas of the globe, rivers are simulated to be either losing or gaining, depending on the parameter combination, indicating a high uncertainty in simulating the direction of flow between the two compartments. Mountainous and dry regions show a high variance in simulated head due to numerical instabilities of the model, limiting the reliability of computed sensitivities in these regions. This is likely caused by the uncertainty in surface water body elevation. We conclude that maps of spatially distributed sensitivities can help to understand the complex behavior of models that incorporate data with varying spatial uncertainties. The findings support the selection of possible calibration parameters and help to anticipate challenges for a transient coupling of the model.

In global hydrological models, groundwater (GW) is typically represented by a bucket-like linear groundwater reservoir. Reservoir models, however, (1) can only simulate GW discharge to surface water (SW) bodies but not recharge from SW to GW, (2) provide no information on the location of the GW table, and (3) assume that there is no GW flow among grid cells. This may lead, for example, to an underestimation of groundwater resources in semiarid areas where GW is often replenished by SW or to an underestimation of evapotranspiration where the GW table is close to the land surface. To overcome these limitations, it is necessary to replace the reservoir model in global hydrological models with a hydraulic head gradient-based GW flow model. We present G3M, a new global gradient-based GW model with a spatial resolution of 5′ (arcminutes), which is to be integrated into the 0.5∘ WaterGAP Global Hydrology Model (WGHM). The newly developed model framework enables in-memory coupling to WGHM while keeping overall runtime relatively low, which allows sensitivity analyses, calibration, and data assimilation. This paper presents the G3M concept and model design decisions that are specific to the large grid size required for a global-scale model. Model results under steady-state naturalized conditions, i.e., neglecting GW abstractions, are shown. Simulated hydraulic heads show better agreement to observations around the world compared to the model output of de Graaf et al. (2015). Locations of simulated SW recharge to GW are found, as is expected, in dry and mountainous regions but areal extent of SW recharge may be underestimated. Globally, GW discharge to rivers is by far the dominant flow component such that lateral GW flows only become a large fraction of total diffuse and focused recharge in the case of losing rivers, some mountainous areas, and some areas with very low GW recharge. A strong sensitivity of simulated hydraulic heads to the spatial resolution of the model and the related choice of the water table elevation of surface water bodies was found. We suggest to investigate how global-scale groundwater modeling at 5′ spatial resolution can benefit from more highly resolved land surface elevation data.

As a special class of materials, transition metal oxides exhibit in their crystalline phase a variety of interesting properties, such as metal–insulator transition, ferroelectricity, magnetism, superconductivity, and so forth. However, for industrially widely applied methods such as room temperature magnetron sputtering, during initial fabrication steps of these materials, they are mostly amorphous, and control of stoichiometry during fabrication is challenging. It is, therefore, of pivotal importance to control the stoichiometry of transition metal oxides during growth in the amorphous state. One particularly important example for the necessity of stoichiometry control is vanadium dioxide (VO2), where small deviations in stoichiometry during fabrication result in unfavorable changes in the electronic and structural properties, for example, the metal–insulator transition temperature and optical permittivity. In this work, the stoichiometry of amorphous vanadium oxides is adjusted to VO2 using in situ spectroscopic ellipsometry (in situ SE) and verified by x-ray photoelectron spectroscopy. After an annealing process, a monoclinic VO2 crystalline structure is observed through x-ray diffraction at 30 °C. At an elevated temperature of 150 °C, which is higher than the typical metal–insulator transition temperature in VO2 of around 67 °C, a rutile crystalline structure is observed, which verifies the correctness of the stoichiometry of VO2. A Mott metal–insulator transition is revealed by the change in the imaginary part of optical permittivity through SE as well.

The assessment of water balance components using global hydrological models is subject to climate forcing uncertainty as well as to an increasing intensity of human water use within the 20th century. The uncertainty of five state-of-the-art climate forcings and the resulting range of cell runoff that is simulated by the global hydrological model WaterGAP is presented. On the global land surface, about 62 % of precipitation evapotranspires, whereas 38 % discharges into oceans and inland sinks. During 1971–2000, evapotranspiration due to human water use amounted to almost 1 % of precipitation, while this anthropogenic water flow increased by a factor of approximately 5 between 1901 and 2010. Deviation of estimated global discharge from the ensemble mean due to climate forcing uncertainty is approximately 4 %. Precipitation uncertainty is the most important reason for the uncertainty of discharge and evapotranspiration, followed by shortwave downward radiation. At continental levels, deviations of water balance components due to uncertain climate forcing are higher, with the highest discharge deviations occurring for river discharge in Africa (−6 to 11 % from the ensemble mean). Uncertain climate forcings also affect the estimation of irrigation water use and thus the estimated human impact of river discharge. The uncertainty range of global irrigation water consumption amounts to approximately 50 % of the global sum of water consumption in the other water use sector.

When assessing global water resources with hydrological models, it is essential to know about methodological uncertainties. The values of simulated water balance components may vary due to different spatial and temporal aggregations, reference periods, and applied climate forcings, as well as due to the consideration of human water use, or the lack thereof. We analyzed these variations over the period 1901–2010 by forcing the global hydrological model WaterGAP 2.2 (ISIMIP2a) with five state-of-the-art climate data sets, including a homogenized version of the concatenated WFD/WFDEI data set. Absolute values and temporal variations of global water balance components are strongly affected by the uncertainty in the climate forcing, and no temporal trends of the global water balance components are detected for the four homogeneous climate forcings considered (except for human water abstractions). The calibration of WaterGAP against observed long-term average river discharge Q significantly reduces the impact of climate forcing uncertainty on estimated Q and renewable water resources. For the homogeneous forcings, Q of the calibrated and non-calibrated regions of the globe varies by 1.6 and 18.5 %, respectively, for 1971–2000. On the continental scale, most differences for long-term average precipitation P and Q estimates occur in Africa and, due to snow undercatch of rain gauges, also in the data-rich continents Europe and North America. Variations of Q at the grid-cell scale are large, except in a few grid cells upstream and downstream of calibration stations, with an average variation of 37 and 74 % among the four homogeneous forcings in calibrated and non-calibrated regions, respectively. Considering only the forcings GSWP3 and WFDEI_hom, i.e., excluding the forcing without undercatch correction (PGFv2.1) and the one with a much lower shortwave downward radiation SWD than the others (WFD), Q variations are reduced to 16 and 31 % in calibrated and non-calibrated regions, respectively. These simulation results support the need for extended Q measurements and data sharing for better constraining global water balance assessments. Over the 20th century, the human footprint on natural water resources has become larger. For 11–18% of the global land area, the change of Q between 1941–1970 and 1971–2000 was driven more strongly by change of human water use including dam construction than by change in precipitation, while this was true for only 9–13 % of the land area from 1911–1940 to 1941–1970.

ENGLISH ABSTRACT: The dynamics of a typical production-distribution system, namely from manufacturer to distributors to retailers has been simulated with the aid of Lotus 123 on a personal computer. The original simulation program DYNAr10 was run on an IBM 1620 mainframe computer but we successfully converted it to run on a personal computer using LOTUS 123.This paper deals with problems encountered in using the present MS-DOS limited PC machines to run application programmes written for earlier mainframe machines. It is also shown that results very comparable with those obtained on mainframe machines can be generated on a simple PC.AFRIKAANSE OPSOMMING: Hierdie referaat beskryf die ervaring van magisterstudente met die omskakeling van die simulasieprogram DYNAMO vir die ondersoek van die dinamika van industriele stelsels van hoofraamrekenaar na 'n persoonlike rekenaar.

This paper provides an introduction to the most commonly used Knowledge Based Systems (KBS's) called Rule Based Systems, presents some benefits of using these systems if the application warrants their attention and provides an over-view of current R&D as well as industrial systems already implemented. Areas of manUfacturing that could use KES's within the South African context are suggested. A research programme investigating the use of KBS's in robotics in progress at the University of Stellenbosch demonstrating a number of useful properties associated with programming Artificial Intelligence (AI) techniques using logic programming, is discussed.

ENGLISH ABSTRACT: The Centre for Robotics at the University of Stellenbosch set itself the objective of building a fairly complex manufactu.ring ceH, including .'.11 unskilled human as a system componenL As a precursor to this effort we constmcted a simple cell requiring both supervision of a robot and supenision of a human using a Micro-Prolog knowledge system to do so. l1tis was successfully done but at the costar low execution speed and difficulty in integrating machine code instructions for machine control interfacing with the largely consultation orientated softv,are which rendered the approach unsuitable fortbe more complex cell. MiCroExpert "..as used for this new effort but we a1sa tried Turbo-Prolog 10 mimick the inference engine of the former software. This experience made us decide 10 trade the higher speed achieved by Turbo-Prolog for the much more rapid knowledge base development in MicroExpen. To do so it was necess::.uy to bulld a special frame data sLrUtTille and to enhance. Micro-Expert for supervising such manufactlrring cells.AFRIKAANSE OPSOMMING: Die Seotrunl vir Robotika aan die Universiteit van Stellenbosch is die taak gestelam'n komplekse vervaardigingsel to bOll wat 'n ongeskoolde mens as stelselkomponent sou moes insluiL As voorloper vir hierdie paging het ons eers 'n eenv0udige scI daargeste! waarby loesig oar sJeg 'n robot en 'n mens nodig v.'as deur IT'JddeJ van 'n kcn..IDsste!sel gegrond op Micro-Prolog. Oit was suksesvol maar len koste van betreklike lae ultvaerspoed en omslagtige instruksies in masjienkode vir die toesig oor die robot 5e werking, met die progranllnatuur was eintlik toegesr.its is op diagnose en konsultzsie. Ter'J''Y1 hierdie paging geslaagd was was dil duideltk dat die benadering nie so suhesvol op die beplance komplekse scI sou wees nie. Daarom is MicfoExpert aangewend vir die finale sel waarby OTIS verder Turbo-Prolog gebruik het om die infercnsie-enjin van Micro··Prolog na Ie boots_ Hierdie ervaring het gelei tot die besluit om die huidige hoer spoed van Turbo-Prolog in te boet vir die gema.!{ waarmee die ontwikkeling van kel1l1.isstelsels in Micro-E)[pert gedoen kan word. Die gebruik van Microfu'Pert vIr die besondere toepassiug het ous egter genoodsaak om 'n spesiale raam datastruktuur daar te stel en am l(licrofu'Pert verder uit te bOlL

Knowledge Based System (KBS) technology emanating from a sub-field of Artificial Intelligence can be a powerful and yet deceptive engineering tool. It's power is evident from the magnitude of published KBS applications. It's deceit lies in the illusion that the technology is universally powerful and relatively simple to implement. This paper attempts to aid the engineer with the handling and application of this new tool : by firstly presenting an overview of the historical evolution of KBS's and describing their organisation, and secondly, by describing a number of successful engineering applications of KBS's. Common deceptive pitfalls and simplifications are exposed at each step.

Real-world problems often do not lend themselves to an algorithmic solution. Humans, however, cope with these problems despite their fallible problem solving techniques. Instead of trying to construct algorithms to solve problems AI researchers have concentrated on using the more successful methods used by humans. This paper reviews the area of problem solving in the field of Artificial Intelligence. This includes problem representation for computation, "weak" methods of searching for a problems solution, knowledge representations that facilitate more efficient search strategies and planning - an advanced problem solving technique.

This article reports on a study conducted on several important parameters in a real-life problem of asset replacement. A study of the literature revealed the relevant parameters. A spreadsheet programme was created to find an optimum replacement strategy for fork-lift trucks. This same programme was then used for a sensitivity analysis on the most important parameters. The results of this analysis are discussed in this paper. A short user's manual as well as some notes on the working of the program is included.

The programme suit TEMPOS is an aid to medium-term forecasting of national major economic time series. It is based on the assumption that the well-known recurrent, but non-periodic business cycles can be represented by simple but strictly periodic cyclic movements, each driven by a separate but not necessarily known external economic factor. As the elements of such a model are individually extrapolatable, the model as a whole may be extrapolated over a limited horizon. Die suite rekenaarprogramme TEMPOS is 'n hulpmiddel vir vooruitskatting in die mediumtermyn van nasionale omvang ekonomiese tydreekse. As uitgangspunt geld die aanname dat die bekende herhalende maar nie-periodieke konjunktuurgolwe voorgestel kan word deur eenvoudiger maar streng periodieke golwe, elk gedrewe deur eiesoortige eksterne ekonomiese faktore.

For centuries, mountain grasslands have been part of the grazing cycle of sheep and cattle in extensive management systems in the Pyrenees; however, traditional guided herding has been, in many cases, replaced by free-ranging flocks at these pastures. The goal of this study was to analyze the grazing behavior of free-ranging sheep in mountain pastures using GPS-based tracking systems and Geographic Information Systems. During the summer seasons of 2019, 2020, and 2021, a transterminant flock of free-ranging sheep was tracked with GPS devices attached to collars at the mountain pastures of Collarada mountain (Central Pyrenees, Spain). Preferences for grazing on certain geomorphological features (slope, aspect, and altitude) and different plant communities present in the area were evaluated using the Manly's standardized preference index. The results show that sheep prefer altitudes between 2400 and 2600 m; SE-, SW-, and E-facing sites; and slopes under 20%. The preferred pastures were Festucion eskiae , Primulion intricatae , and Nardion strictae ; however, they reject Festucion scopariae communities. This study demonstrates the effectiveness of GPS and GIS technologies in monitoring free-ranging sheep activity, providing valuable data for enhancing pastoral practices and ensuring sustainable pasture use.

The studied farms are small family businesses, and so, in more than half of the cases, their continuity is not guaranteed. Livestock management is typical of a mountain system, in which the animals graze throughout the year in cultivated fields, sown meadows, forests near the farms, and mountain pastures during the three summer months. The herds always have the constant surveillance of a shepherd. Farmers consider the current infrastructure present in mountain grasslands insufficient to facilitate the management and care of their herd. Their activity conflicts with various species of wildlife, such as the wild boar, Sus scrofa , roe deer, Capreolus capreolus , or griffon vulture, Gyps fulvus , and large carnivores such as the brown bear, Ursus arctos , or the grey wolf Canis lupus , despite all of them taking preventive measures to defend their herds from predators. The most widely used prevention measures are the presence of mastiff dogs, Canis lupus familiaris , next to the herds and the use of electric fencing to lock up livestock at night. Farmers reject the presence of bears and wolves in their area, considering it a real threat to the continuity of their economic activity, which presents a high degree of vulnerability., Competing Interests: The authors declare no conflict of interest.

Background and Aims: European mesic meadows are semi-natural open habitats of high biodiversity and an essential part of European landscapes. These species-rich communities can be a source of seed mixes for ecological restoration, urban greening and rewilding. However, limited knowledge of species germination traits is a bottleneck to the development of a competitive native seed industry. Here, we synthesize the seed ecology of mesic meadows., Methods: We combined our own experimental data with data obtained from databases to create a combined dataset containing 2005 germination records of 90 plant species from 31 European countries. We performed a Bayesian meta-analysis of this dataset to test the seed germination response to environmental cues including scarification, stratification, temperature, alternating temperature and light. We also used multivariate ordination to check the relationship between seed traits (germination and morphology) and species ecological preferences, and to compare the seed ecology of mesic meadows with that of other herbaceous plant communities from the same geographic area., Key Results: The seed ecology of mesic meadows is characterized by (1) high seed germinability when compared with other herbaceous plant communities; (2) low correspondence between seed traits and species ecological preferences; and (3) a deep phylogenetic separation between the two major families, Poaceae and Fabaceae. Poaceae produce many light seeds that respond to gap-detecting germination cues (alternating temperatures and light); Fabaceae produce fewer heavy seeds, which need scarification to break their physical dormancy., Conclusions: High germinability of meadow seeds will reduce their capacity to form persistent seed banks, resulting in dispersal limitations to passive regeneration. For centuries, human activities have shaped the regeneration of meadows, leading to a loss of seed dormancy and decoupling seeds from seasonal cycles, as has been found in many domesticated species. The same anthropic processes that have shaped semi-natural mesic meadows have left them dependent on continued human intervention for their regeneration, highlighting the importance of active restoration via seed supply., (© The Author(s) 2021. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)